1. Field of the Invention
This invention is concerned with the manufacture of ethylene from a methanol feed. It is particularly concerned with the catalytic conversion of a methanol feed to a hydrocarbon mixture of high ethylene content.
2. Description of the Prior Art
A remarkable growth in the production of synthetic fibers, plastics and petrochemicals has taken place in recent decades. This growth, to a very large extent, has been supported and encouraged by an expanding supply of inexpensive petrochemical raw materials such as ethylene, propylene, and other lower olefins. The principal raw material for ethylene at the present time is petroleum naphtha, which is steam cracked to produce a mixture of products from which ethylene is recovered. A large fraction of this ethylene is used in the manufacture of polyethylene and styrene monomer.
The burgeoning demand for olefins has of course led to periods of shortage, due either to short supply of suitable petroleum feedstocks or to limited processing capacity. It is obviously desirable to provide efficient means for manufacturing ethylene from raw materials other than petroleum.
U.S. Pat. No. 4,025,575, Ser. No. 566,166 filed Apr. 8, 1975 describes a process by which lower alcohols and/or their ethers are converted to a mixture of C.sub.2 to C.sub.5 olefins by contact at subatmospheric inlet partial pressure with a crystalline aluminosilicate zeolite catalyst having a constraint index of 1 to 12 and a silica to alumina ratio of at least 12.
The production of olefins from aliphatic ethers by catalytic conversion with, e.g., a HZSM-5 zeolite catalyst is described in U.S. Pat. No. 3,894,106 issued July 8, 1975.
The use of diluents to dissipate exothermic heat in a two stage conversion of methanol to gasoline is described in U.S. Pat. No. 3,931,349 issued Jan. 6, 1976.
A two stage conversion of a lower alcohol to olefins or to gasoline, which process employs a tubular reactor for the second stage is described in U.S. Pat. No. 4,058,576, Ser. No. 720,870 filed Sept. 7, 1976.